1. Statement of the Technical Field
The inventive arrangements relate generally to methods and apparatus for multi-band antenna operation, and more particularly for dynamically changing the operational characteristics of an antenna.
2. Description of the Related Art
A wide variety of RF antenna elements are commonly manufactured on dielectric substrate. These include common dipole antenna elements as well as a variety of patch type antennas. The band of frequencies over which such antennas will function is largely determined by the geometry of the antenna element, ground plane spacing and characteristics of the dielectric substrate on which the antenna is formed. In many types of antenna element, antenna impedance changes significantly with frequency. This results in an impedance mismatch to the feed line when the antenna is operated outside a relatively narrow operational bandwidth. If the impedance of different parts of the circuit do not match, this can result in inefficient power transfer, unnecessary heating of components, and other problems. Consequently, the antenna element may not be usable except over a relatively narrow range of operating frequencies.
Two critical factors affecting the performance of the dielectric substrate material are permittivity (sometimes called the relative permittivity or ∈r) and permeability (sometimes referred to as relative permeability or μr). The relative permittivity and permeability determine the propagation velocity of a signal, which is approximately inversely proportional to √{square root over (μ∈)}. These same factors affect the electrical length of an antenna element. Since antenna elements are typically designed to be a particular geometry and size relative to the wavelength of the operating frequency, the choice of the substrate material affects the overall size of the antenna element.